Method of producing a mixed liquid fertilizer containing nitrogen and phosphorus



April 21, 1 w. R. STEPHENS METHOD OF PRODUCING A MIXED L IQUID FERTILIZEPHOSPHORUS CONTAINING NITROGEN AND Original Filed Nov. 28, 1956 2Sheets-Sheet 1 INVENTOR. will E. sfeplzerzs yfl itz cliiarneys v 9% o aNLmBMQuQ l 1964 w. R. STEPHENS 3,130,033 METHOD OF PRODUCING A MIXEDLIQUID FERTILIZER CONTAINING NITROGEN AND PHOSPHORUS Original Filed Nov.28, 1956 2 Sheets-Sheet 2 INVENTOR. will KSiepkens BY @m0 4% fi 7%"diiprneqs I United States Patent METHOD OF PRODUCiNG A MIXED LIQUIDFERTILEZER CQNTAINING NITRGGEN AND PHOSPHGRUS Will R. Stephens, CedarRapids, Iowa, assignor to Barnard & Leas hianufacturing Company, 1112.,Cedar Rapids, Iowa Original application Nov. 28, "1956, Ser. No.624,840, now Patent No. 2,977,201, dated lVIar. 28, 1961. Divided andthis application Aug. 30, 1960, Ser. No. 52,974

11 Claims. (Cl. 711) This invention relates broadly to the admixture offluid components under controlled conditions for combination or reactionand to a system or apparatus capable of use in continuous operation forthe preparation of a desired fluid product in an efficient andeconomical manner.

More specifically, it relates to the preparation of a mixed liquidfertilizer by admixture of the various components from solutions in acontinuous operation thereby to enable manufacture at low cost and atseparated stations for local distribution.

This application is a division of application Ser. No. 624,840, filedNovember 28, 1956, now Patent No. 2,977,201, patented March 28, 1961,entitled Method and Apparatus for Producing Liquid Reaction Products.

While various concepts of this invention have application to theadmixture of any two or more fluids for combination or reaction, theconcepts of this invention are of particular interest in the preparationof a liquid fertilizer system, such as aqueous ammonia, or preferablymixed fertilizers formed of ammonia and phosphoric acid present incombination in the desired ratio to produce a new and improved neutralfertilizer and which may be diluted with water to a desiredconcentration for local distribution and use. As a result, the inventiveconcepts which will hereinafter be described will have applicationparticularly to a system for the manufacture of a mixed liquidfertilizer but it will be understood that many of the concepts that willhereinafter be described can be employed equally well for thecombination or reaction of other components in a liquid state to producea desired finished product.

On practically every piece of land throughout the world which is tilledfor agricultural or growing purposes, use is made of a fertilizer tosupplement the elements found to be desirable in the earth for best usein the growth of various products. In this way, pieces of land arereclaimed for agricultural purposes while other pieces of land areimproved or retained in a desirable condition for maximum yield of grownproducts. For the most part, use has been made of a dry mixturecontaining the various elements in the form of compounds from which theelements can be released by reactions that take place in the soil. Suchdry fertilizer mixtures are fairly expensive from the standpoint of thematerials of which they are formed, their admixture one with the otherfor uniform distribution of the compounds, and from the standpoint ofthe cost for transportation from the source of manufacture to distantpoints of use. In addition, the elements in the dry fertilizer intendedto be made available in the soil are tied into their respectivecompounds in a manner which often resists immediate release. As aresult, dry fertilizers are generally considered to be slow acting inthe release of their components for supplementing the elements necessaryfor plant growth.

More recently liquid fertilizers have been developed for use in place ofdry fertilizer mixtures for enrichment of the soil. When applied as aliquid fertilizer, the elements present in solution in the compositionare made almost immediately available in the soil for utilization3,130,033 Patented Apr. 21, 1964 in growth. In addition, the liquidfertilizer systems are more easily spread as by spraying or sprinklingover the soil thereby to enable the use of less expensive equipment andless time. Because uniform distribution is a characteristic of liquidsystems, preparation of the liquid fertilizer for distribution can bemade Without the extensive equipment required for mixing, blending andpackaging the dry fertilizers and with the result that formulation canbe effected at stations from which local distribution can be madewithout the necessity to transport substantial components of thefertilizer mixture, such as water. These all lead to the greateracceptability which is being enjoyed by liquid systems as compared todry mixtures for fertilizing the soil.

To the present, liquid fertilizer systems have been formulated primarilyon a batch principle wherein each of the components have been weighedinto a mixing tank from storage containers with the result that a largeinventory in materials, equipment and space is required for the storageof the raw materials, for the batch mixing of the raw materials, and forthe storage of finished product for distribution. In addition, thenumber of units is proportionately increased by the number offormulations which are prepared containing various ratios of nitrogen,

' phosphorus and the like, and various concentrations there of. As aresult, the investment in materials and equip ment has indirectly beenreflected in the cost of liquid fertilizers with the result that dryfertilizer systems have remained competitive and, in some instances, thedry fertilizer mixtures have even enjoyed an economical advantage overliquid fertilizers.

Further, liquid fertilizer systems which have heretofore been producedhave been acidic in character because of the necessity to incorporatethe phosphorus as phosphoric acid in substantial amounts. Such acidicsystems lead to serious corrosion problems in the equipment processingthe fertilizer and in handling the fertilizer further to interfere withthe wide-spread acceptance of liquid materials as a replacement for thedry mix fertilizers.

It has been found still further that unless a fairly pure grade ofphosphoric acid is employed for admixture and reaction with ammonia inthe manufacture of ammonium phosphate, the impurities present in theacid tend to form insoluble products that settle out of the solution andinterfere with the flow of the wet mix and in the uniformity of thecomposition thereof. Such pure acids of furnace grade are not only moreexpensive than the less pure red oil grade but the impurities in red oilhave been found to be beneficial to the soil. As a result, while thelower cost acid would be more desirable from a nutrient as Well as froma cost standpoint, the difiiculties resulting from separation in usehave necessitated the use of the less desirable and more expensivematerials. These further lend to the advantage of the dry mixfertilizers over liquid systems.

It is an object of this invention to provide a method and apparatus forovercoming the many disadvantages and limitations heretofore encounteredin liquid fertilizer systems and to make liquid fertilizers readilyavailable at lower cost to the user and to make available an improvedliquid fertilizer which is competitive, if not more desirable, from thestandpoint of cost and composition by comparison with the dry mixfertilizers.

In general, it is an object of this invention to provide a method andapparatus for bringing together various liquids containing chemicals insolution for diffusion, combination or reaction and it is a relatedobject to effect the desired diffusion, combination or reaction withcomponents containing one or more vaporizing compounds to produce astable product without the dangers characteristic of the formation ofvolatilizable materials.

Another object is to provide a method and apparatus whereby variouschemical solutions can be processed through various operations from thesupply to the final product in condition for storage or distributionincluding the removal, measurement, diffusion, reaction, anddistribution or storage, without exposure of the operating per sonnel tocontact with the various materials and mixtures, and it is a relatedobject to carry out the combination of steps for such processing withaccuracy that is required to produce an acceptable finished product.

It is an object to provide a means of the type described for processingvarious chemical liquids from their respective sources of supplyincluding accurate measurement, diffusion, reaction and storage, in acontinuous operation whereby the need for storage facilities for the rawmaterials and for the finished product can be reduced to a minimum andwhereby the process can be carried out in various locations where thelargest proportion of materials can be made available at low cost forlocal distribution directly to the user.

A still further object is to provide a means for the safe and efiicientcombination of materials which react exothermically and which operatesautomatically to control such combination to produce a neutral systemthat avoids the objectionable characteristics of corrosion such asprevailed in wet mix fertilizer systems heretofore formulated of ammoniacompounds and phosphoric acid.

A still further object is to provide a means and apparatus of the typedescribed which is capable of continuous operation for combining variousmaterials in solution and which is of such simplicity in constructionand operation as to enable transportation for use at various stationsthereby to make the processing equipment available for. use at thesource for supply of the bulkier materials and which enables location ofthe equipment adjacent the means for making available the less bulkymaterials which are shipped in, such for example as adjacent the highwayor trackage for receiving the ammonia or phosphoric acid or the likechemicals thereby materially to reduce the cost to the consumer.

Another object is to provide a means for effecting diffusion offertilizable chemicals in solution without enabling gas or vaporformation or the development of other conditions which might lead toexplosion or danger and it is a related object to provide a means of thetype described for causing diffusion or reaction in a manner to producea new and improved product from which separation characteristic of othermeans for admixture for combination is avoided.

More specifically, it is an object of this invention to provide a lowcost and easily transportable mechanism as a unit operation to produceneutral chemical fertilizers hear the area of use and in a formimmediately available to'plants as a nutrient and which will not injurethem upon contact.

It is a further specific object to provide a unit mechanism of the typedescribed for converting potent chemicals into a neutral liquidfertilizer of a controlled and predetermined chemical content inconformity with standard agricultural chemistry formulae, and which canbe universally applied with inexpensive equipment by farmers or othernonspecialized personnel.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, an embodiment of the invention is shown in the accompanyingdrawings in which- FIGURE 1 is a flow diagram of the system embodyingthe features of this invention;

FIGURE 2 is a sectional view of the mixer section wherein the liquidmaterials are combined, difiused or reacted one with the other;

FIGURE 3 is an enlarged sectional view taken along the line 3--3 ofFIGURE 2, and

FIGURE 4 is an enlarged sectional view taken along 7 the line 4-4 ofFIGURE 2.

tilizer containing a desired predetermined balance between nitrogen,introduced from anhydrous or aqueous ammonia solution, and phosphorus,introduced in the form of phosphoric acid, and the like phosphoric acidsand salts thereof. The materials are combined by a proportioner whichcan be preset to control the amount of phosphoric acid and water toprovide for a certain concentration of phosphorus in the final product.The ammonia component is added in an amount which is respon sive to thepH of the mixture to provide for a neutral solution having a pH of about6.8. These controls for measurement of each of the ingredients operateautomatically to compensate for the changes in raw materials employed orconditions existing in operation which otherwise might normally vary thein-put of raw materials. Thus it becomes possible to maintain constantcontrol for a continuous operation to produce a uniform product ofpredetermined chemistry. It will be understood that the system describedcan be employed for the combination of raw materials in otherpredetermined ratios for phosphorus and nitrogen or for the preparationof aqueous ammonia by dilution of anhydrous ammonia or for theadmixture, diffusion or reaction of other chemical compounds to producea liquid product capable of measurement and control.

For a general review first of the concepts of this invention as embodiedin a commercial system, reference will be made to the flow diagram ofFIGURE 1 for the production of a mixed liquid fertilizer. The numeral 10represents a passage in the form of a pipe for the flow of phosphoricacid under pressure from a supply source (not shown) to a mixer device12 which will hereinafter be described. A pump of conventional design(not shown) is embodied in the line for causing fluid to flow and avalve 14 is provided for opening and closing the passage in advance ofan orifice plate 16 for measuring the flow of phosphoric acid.

The numeral 18 represents another passage in communication with asuitable pump for circulating ammonia under pressure from a suitablesupply source to a portion of the mixer device 12 beyond the inlet forthe phosphoric acid. A suitable shut-off valve 20 is also provided inthe line in advanceof an air controlled valve 22 which controls the rateof flow of ammonia.

The numeral 24 represents a third passage through which water iscirculated under pressure, as by a pump (not shown) from a local supplysource such as a well, to the inlet end of the mixer 12 in advance ofthe inlet for the phosphoric acid or ammonia. A shut-off valve 26 isprovided in the water line in advance of an air controlled valve 28which operates to regulate the flow of water. The valve is also providedin advance of an orifice plate 30 which measures the rate of flow of thewater.

The source of supply for the phosphoric acid and ammonia may comprisestationary reservoirs but it is preferred to minimize requirements forstorage space and equipment by making use of the tanker itself as asupply source for such materials thereby to enable portable units to beconstructed for location adjacent trackage or a road over which thetankers may be moved. This is made possible by the continuous flowprocess which will hereinafter be described embodying equipment that canbe assembled on a platform for transportation from station to stationfor the local supply of mixed fertilizer to farmers for use and whichmakes use of a local supply of water as one of the major ingredients tominimize the cost for shipment of a material which might otherwise beformed principally of this ingredient.

Both the phosphoric acid and water are continuously fed under pressurethrough their respective passages 10 and 24 for diffusion or admixturein the mixer device 12 in a predetermined ratio, as will hereinafter bedescribed, for producing a concentrated solution of a mixed fertilizer.The ammonia is fed under pressure into a subsequent portion of the mixerdevice for combination and reaction with the phosphoric acid solution toproduce an arnmonium phosphate. The amount of ammonia is balanced toreact with the phosphoric acid to produce a fertilizer having a pHwithin the range of 69 but which is preferably controlled to produce aneutral fertilizer having a pH of about 6.8.

The combined fluids are advanced through a passage 32 from the outlet ofthe mixer 12 into a spray head 34 of a reaction tank 36 where thematerials are able to complete their reaction prior to circulationthrough a cooler section 49 for the extraction of some of the heatdeveloped by the exothermic reaction. From the reactor tank 36, thematerial is circulated under pressure by the pump 42 through thepassages 44 and 46 to the header The header distributes the fluid forhow through the fins 5t? which wind back and forth over the surface ofbanks of cooling plates 52 which are cooled on their outside by streamsof water 5 sprayed onto the surface by spray pipes 56.

The amrnonium phosphate solution flows from the outlets 58 of thecooling plates into headers 69 and to a collecting pipe 62 wherein thecooled material is separated at 64 into one portion which isrecirculated through passages 66 for combination with the hot liquidcoming from the mixer 12 prior to introduction into the reaction tank 36while the remainder of the product is caused to flow through passage 63to a storage tank or to a waiting tanker for local distribution and use.

Having briefly described the flow of materials, description will now bemade of the various concepts of this invention which are embodied in thenew and improved system for the continuous and efiicient preparation ofa mixed liquid fertilizer and for control to produce a balancedfertilizer of uniform composition and which operates further to avoidthe development of conditions in operation which would lead either tothe existence of dangerous conditions or loss of materials. The systemdescribed permits the utilization of less expensive and more desirablematerials in manufacture thereby to produce a better and less expensivemixed liquid fertilizer.

Referring first to the controls for maintaining the constant balancebetween the amount of water mixed with phosphoric acid, it has beenfound best to maintain the desired ratio by adjustment of the flow rateof the water under pressure while maintaining the rate of flow ofphosphoric acid as constant as possible. For this purpose, the orificeplate 16 is provided in the phosphoric acid line immediately in advanceof entrance into the mixer 12 and a similar orifice plate St) isprovided in the water line 24.

When use is made of the orifice plates of the type described,displacement pressure cells are located on the upstream or downstreamside of the orifices to record the pressure diflerential. The cellsoperate through an air line 7%) to transmit changes in pressure due tochanges in the rate of flow to a controller 72. As the pressure changesin response to the differential, a corresponding change is caused to berecorded in the controller which operates through line 74 to effectopening and closing movements of the air controlled valve 23 in thewater line. The control is usually set for a predetermine pressuredifferential. The air controlled valve in the water line is maderesponsive to the ratio flow controller 72 to increase or decrease therate of how of water responsive to deviation in the flow rates of waterand phosphoric acid. Suitable orifice plates or other sensing means formeasuring the rate of fiow are well known in the art and equivalentcomponents may, if desired, be substituted for the orifice plates.Pressure responsive controllers are also known for operation of a valveto open and close the valve in response to results from the recorder.

The amount of ammonia added is calculated, in preferred practice of thisinvention, to neutralize the phosphoric acid to produce a neutralfertilizer having a pH of about 6.8. Because of the wide variation indensity the of ammonia responsive to temperature changes, it isdifficult to rely upon a volumetric means to control the rate of flow tomaintain the desired ratio between the amount of ammonia and phosphoricacid. As a result, it is a further concept of this invention to embody ameans for controlling the amount of ammonia added to the system inresponse to the pH of the final product. For this purpose, there isprovided a pH controller in the form of a Beckman pH meter or the likehaving its sensing point 82 located in the product line to measure thepH of the product flowing from the cooling section. The air controlvalve 22 in the ammonia line 18 is adapted to be operated by the pHrecorder controller to open or close the valve in response to variationin pH of the product from a predetermined level.

The ammonia component can be incorporated into the system as ananhydrous material or in the form of a water solution such as ammoniumhydroxide. When use is made of ammonia in solution in water it ispreferred to make use of a composition containing less than 25 percentNH While higher concentrations of NH can be employed, solutionscontaining more than 25 percent require positive pressure to preventvaporization of the ammonia. As the lower concentration, it is preferredto make use of a solution containing more than 10 percent by weight NHand preferably the amount of ammonia in solution is maintained withinthe range of 16-25 percent by weight.

The phosphoric acid and ammonia combine in an exothermic reaction toproduce an ammonium phosphate (NHflPO In formulation of a concentratedfertilizer, such for example as a fertilizer containing 9.76 percent byWeight NH 44 percent by weight H PO and 46.26 percent by weight water,as in the preparation of an 8-24-0 liquid fertilizer, the heat ofreaction is sufiicient to raise the temperature of the materials toabove 200 F., depending somewhat upon the temperature of theingredients. In this temperature range, there is a possibility of boilinofi of ammonia vapors or other gases from the material and also ofboiling off some of the liquid. Volatilization of ammonia or moistureraises dangerous conditions not only with respect to the loss of ammoniainto the atmosphere but pressure conditions leading to explosion or thelike also become possible. As a result, an important concept of thisinvention resides in the means rapidly to decrease the temperature ofthe materials immediately upon diffusion and combination one with theother in a continuous operation.

In accordance with the practice of this invention, the materialscombined in the mixer 12 are immediately in troduced into a reactionchamber with expansion from the elevated temperatures of reaction toabout atmospheric pressure thereby to achieve, in part, a reduction intemperature. Simultaneously, a substantial proportion, such as about 75percent, of the product from the cooling section is recirculated throughthe passages 66 for combination with the hot material issuing from themixer 12 thereby immediately to achieve a reduction in temperature to alevel below that at which vaporization or volatilization can take placein any substantial or uncontrolled amounts.

In practice, the material from the mixer issuing at about 210 F. iscombined with about three times its weight of product liquid from thecooler at about F. thereby to reduce the temperature of the liquid fedinto the reaction chamber to about F. At this temperature, release ofammonia vapors is minimized and evaporation of moisture is substantiallyeliminated. The fluid under pressure is expended through the valve 34into the reaction chamber to achieve a still further reduction intemperature and to enable further reaction of components which mightpreviously have escaped completiOn of the reaction. Usually the reactionbetween the ammonia and phosphoric acid will have been completed priorto flow from the mixer as will hereinafter 7 be described so that thereaction tank serves mainly as a collector tank for admixture of theproduct material with fresh material for blending to produce a moreuniform and controlled product for marketing.

The pump 42 raises the pressure of the fluid issuing from the reactiontank to the pressure of the fluid issuing from the mixer device 12 forcirculation of the fluid under pressure to the header 48 and through thefins 50 of the cooling plates and back to the header 60 for collectingthe cooled liquid which is then subdivided into one portion which is ledto storage while the other is recirculated for combination with thefluid issuing at corresponding pressure from the mixer section.

Heat is extracted from the reacted fluid circulated through the fins 50by means of a fluid, such as water 54, which is sprayed onto the outerwalls of the cooling plates. For this purpose, pipes 84 are providedendwise of the cooling plates to extend crosswise of the plates withspray nozzles 56 directly inwardly to throw water onto the plates. Inthe illustrated modification, the spray pipes 56 are located to wet thelower half of the plates but it will be understood that the spray pipesmay be located in other positions and that more than one bank of spraypipes may be employed or that the pipes may extend inwardly from thecross headers 84 through the space between the plates to wet theadjacent surfaces thereof. The water 86 drains from the platesdownwardly into a collection tank 88 at the bottom side of the coolinghousing for collecting the water for re-use, especially where water isat a premium in the more arid areas of the country. A pump 90 operatesto withdraw the water from the pump through an inlet pipe 92 forcirculation through passages 94 to the spray headers. The level of thewater in the pump is controlled by a suitable float mechanism 96 tomaintain the water at the desired level. Where water is not at a premiumor Where a plentiful supply of cold water is available, the watersprayed onto the tanks of cooling plates can be discarded by drainagefrom the equipment.

The temperature of the water may be reduced for cooling by evaporationwhich is caused to take place at an accelerated rate, if desired, by thecirculation of air, as indicated by the arrows 97 through the housing 98of the cooler section, as by means of suction fans 100 located within achimney 102 at the upper end of the housing. An important concept ofthis invention resides in the means and method for combining the water,phosphoric acid and ammonia for reaction in a mixer which minimizes theformation of volatile products or other gases and which causes reactionto take place in a manner and at a'rate which produces a stable systemof materials which otherwise might result in a product in whichseparation and settling would ordinarily take place. While theconditions and apparatus for combination of the ingredients willhereinafter be described in detail with reference to the combination ofwater, phosphoric acid and the combination of the water and phosphoricacid solution with ammonia, as in the continuous preparation of a mixedliquid fertilizer, it will be understood that the conditions and meansdescribed will have application as well for the combination of any twosuch materials in solution, such as anhydrous ammonia and water, or anytwo, three, four or more other chemical compounds in a fluid systemwhich are intended to be brought together for reaction to produce afluid product.

Referring now to FIGURES 2-4 of the drawings, the numeral 104 representsan elongate tubular member having a plurality of orifices 106 in theform of jets extending inwardly through the Walls of the tubular memberat an angle to position the inlet end at the outside upstream of theoutlet end in the inner wall of the tubular member. A housing 108surrounds the tubular member with the walls of the housing in spacedrelation with the tubular member to provide an open space 110 all aroundtherebetween. The housing 108 may be of any desired shape but it ispreferred to form the housing of cylindrical section of larger dimensionthan the tubes and arranged concentrically therewith. The space betweenthe tubular member and the housing is formed with a sealing relationtherebetween to enable fluid under pressure to be maintained within theopen space 110 within the housing. The tubular member is formed with aninlet 112 at one end and an outlet 114 at the other. The inletcommunicates with one of the passages through which an ingredient foradmixture is caused to flow under pressure. with an inlet 116 whichcommunicates with the passage for the other fluid for flow of the fluidunder pressure into the housing to keep the space 110 about the tubularmember filled with fluid under pressure. As the first fluid flows underpressure axially from the inlet end to the outlet end through thetubular member an aspirator effect is created which smoothly andcontinuously draws the second fluid under pressure inwardly from theannular space 119 about the tubular member through the jets inclined inthe direction of fluid flow for smooth flow of the second fluid intocombination with the first.

When only two materials are to be combined only a one stage section ofthe type described will be required. When three materials are to becombined, a second station or section of the type described can bearranged in axial alignment with the first with the outlet end 114 ofthe first section in communication with the inlet end 118 of the second.When more than three materials are to be combined in sequence, thenumber of stations or sections can be correspondingly increased.

For purposes of control, an orifice plate'120 is arranged adjacent theinlets and outlets to provide for a pressure drop to control the flow offluids through the tubular members. It is not necessary that thesections be in direct communication one with the other. It will besufiicient if some or all or none of the sections are combined. In fact,spacing may be required in some instances to enable a temporary pausefor reaction of ingredients before further combination to incorporateadditional materials. For purposes of manufacture, however, it isdesirable to make use of orifice plates at the inlet as well as theoutlet for each section. Where the sections are joined, as illustratedin FIGURE 2, a single orifice 1.20 may be employed between the adjacentsections.

In the system described, the water pipe 24 is connected to cause thewater at a pressure, for example at about 85 pounds per square inch, toflow through the orifice plate 129 into the inlet end 112 of the tubularmember 104 for the first mixer step. The phosphoric acid pipe 10 isconnected to the inlet 116 of the housing to introduce phosphoric acidat a pressure, such for example as 20 pounds per square inch. As thewater under pressure flows axially through the tubing from the inlet endto the outlet end, it operates to draw phosphoric acid through the jetopenings 106 for admixture with the water. The outlet end 114 of thefirst mixer section is in communication with an axially aligned orificeplate 120 which leads into the tubular member 104 of the second mixingsection. The ammonia pipe 18 is connected to the inlet 116 of thehousing 108- for introducing ammonium hydroxide solution into thehousing under positive pressure, such for example as at about 80 poundsper square inch. Thus, as the phosphoric acid in water solution flowsaxially through the orifice plate 120* and from the inlet end to theoutlet end of the reaction tube 104 ammonium hydroxide is drawn throughthe jets 106 from the housing into the tubular member for smoothcombination with phosphoric acid solution under positive pressure.

When the ammonia is introduced into the phosphoric acid solution, theexothermic reaction that takes place automatically operates to causesubstantial admixture but the operation is carried out under theconditions de- The housing is provided intermediate its ends' 9 scribedwithout noticeable turbulence thereby to prevent gas formation whichmight otherwise lead to the development of dangerous conditions.

Combination or diffusion of the materials in the manner described underpositive pressure appears to contribute importantly not only to the rateof reaction but to the character of the reaction where reaction not onlytakes place in considerably less time than would ordinarily be requiredfor reaction of corresponding materials under batch conditions but thereaction product formed exhibits a greater stability than is capable ofbeing developed with corresponding materials.

In the first place, the accelerated rate of reaction made possible bythe combination of materials flowing together under positive pressureenables adaptation of the system to a continuous operation as comparedto the batch processes heretofore employed.

Secondly, combination of the materials in continuous fiow together underpositive pressure makes it possible to achieve reaction at anaccelerated rate without gas or vapor formation which otherwise wouldordinarily accomparty the combination of such materials thereby toprovide for better control of the course of reaction and thereby greatlyto improve the safety of the operation.

Thirdly, the combination of materials in continuous flow together fordiffusion or reaction under positive pressure makes available a reactionproduct which appears to be substantially unlike products heretoforesecured by the combination of corresponding materials. This can best beillustrated by the combination of materials in the system described toform a mixed fertilizer but it will be understood that tiow together andreaction under positive pressure will have application as well to thecombination of other liquid reactants.

in the manufacture of a mixed liquid ammonium phosphate, it has beenfound necessary in the past to make use of a relatively pure phosphoricacid which may be identified as furnace grade acid. Such purified acidmarkedly increases the cost of the product to the extent that a mixedliquid fertilizer was at an economic disadvantage by comparison with thedry mixes. Lower grade acids which were considerably less expensive andmuch more available were found to be objectionable because of theprecipitation and settling out which occurred from the higher amounts ofimpurities present in the lower grade material which may be identifiedas red acid. For comparison purposes, a furnace grade acid having onlytraces of impurities costs about $27.00 per 100 pounds whereas red acidhaving as much as 4 percent by weight impurities costs about $6.90 per100 pounds. Obviously the ability to make use of red acid would resultin a considerable reduction in the cost of the liquid fertilizer to theend that an economic advantage could be enjoyed and fuller utilizationcould thus be made of a fertilizer in which the components could be madeimmediately available in the sod for use by the plants.

It has been found in accordance with the practice of this invention thatwhen the materials are diffused and combined under pressure bycontinuous flow together under the conditions described, the reactionproduct that is formed with a red acid appears to be equally as stableas the product that is formed of a furnace grade acid. It appears thatwhatever insoluble materials are formed by the presence of the higheramount of impurities in the red acid remain uniformly suspended in theproduct to the extent that the problems heretofore encountered insettling out and precipitation are not evident in mixed fertilizerliquids prepared under the conditions described. The reason for thisimprovement has not been fully developed but it would appear that theimmediate reaction which takes place under the pressure conditions andflow conditions described causes such insoluble impurities as are formedto be formed in a substantially nascent state in such fine particle formas to cause the product to appear 10 as a clear or pure solution. Thisis to be distinguished from the large amount of settling out that wouldbe experienced by the mixture of exactly the same materials in the sameproportions and under the same temperature conditions in batch systems.

The improvements wln'ch are capable of being secured by the practice ofthis invention in the ability to make use of red acid instead of furnaceacid contributes materially to the improvement in the character of thefertilizer liquid since the impurities in red acid lend materially tothe value of the fertilizer that is formed. Since the acid representsmore than 50 percent of the cost of the final product, it will beevident further that the ability to make use of the lower cost acidmaterially reduces the cost of the final product.

The differences between the reaction product capable of being secured bythe practice of the concepts of this invention as compared to the typeof reactions which have heretofore been employed can be furtherrepresented by the characteristics of a product which goes beyond a pHof 7.0. When the pH of the mixture exceeds this level, diammoniumphosphate or dibasic ammonium phosphate is formed. This material is lesssoluble by a marked degree as compared to the tribasic phosphate withthe result that the dibasic ammonium phosphate ordinarily precipitatesfrom solution. However, when ammonia is incorporated with phosphoricacid in an amount to produce a product having a pH greater than 7.0 oran amount to produce a dibasic ammonium phosphate, little if anycrystallization characteristic of the batch mixture of these materialsis available in the final product even when the product is allowed tostand over a lengthy period of time. Where ammonia is present in suchlarger amounts, one ordinarily would expect free ammonia to rise fromthe hot solution formed by the system. The lack of the availability offree ammonia in the product forme by the practice of this invention hasbeen demonstrated by the use of a scrubber attached to the reactionvessel. No signs of free ammonia were evidenced in the system embodyingthe practice of this invention. This is believed to be indicative of adifference between the reaction products secured by the practice of theconcepts of this invention as compared with other means for combiningmaterials.

The angular relationship of the orifices or jets and lil extendingthrough the tubular member of the reaction vessel can be varied over afairly wide range depending mostly upon the viscosity of the materials.It has been found that the more viscous the materials the steeper theangle. It has been found that the angular relation of the jets should bemaintained within the range of 20-6O degrees and preferably within therange of 22%2-45 degrees. Deviation of the angular relationship of thejets below 20 degrees or beyond 60 degrees tends to reduce the advantageof the venturi action for drawing the one fluid into the other and thepossibility for shock conditions for reaction develops.

The length of the tube is unimportant though it is desirable to balancethe length with the rate of reaction, the rate of flow of materials andthe amount of throughput to achieve the substantial completion of thereaction before clearance of the reaction section by the combinedliquids. If the tubing is too short, one tends to secure a hammer actionand the reaction will not be carried to completion. Lengths beyond theminimum may be em ployed though not necessary when the length issufilcient for completing the reaction. The dimension of the jets mayalso be varied depending upon the amount of through-put. It is preferredto make use of openings as small as possible. The smaller the openings,the more openings that are required for a given through-put ofmaterials.

The pressure conditions existing in the reaction unit can be varied overa fairly wide range from slightly above atmospheric pressure to highpressure limited only by the ability of the structural material towithstand the pressures of operation. It will be understood, however,that often times higher pressures can be used to maintain vapors in acondensed state in the reaction thereby not only to accelerate the rateof reaction but to obviate loss of components which otherwise escape asa gaseous phase or which, in the interim, might present a dangerouscondition in the operation of the process.

It will be apparent from the foregoing that I have briefly described ameans and apparatus for the continuous flow of fluid reactants one intothe other for accelerated reaction to produce an improved product whichhas special application to the manufacture of a mixed fertilizer.

It will be understood that the system described may be utilized tocombine anhydrous ammonia with water to produce aqueous ammoniumhydroxide as a liquid fertilizer for distribution. In such event, onlyone mixer station would be employed and recirculation through a reactorsection could be avoided since an exothermic reaction capable ofdeveloping high temperatures would not be present.

It will be understood that the system described may be adapted for thediffusion, combination and reaction of other liquid chemicals in apredetermined sequence to produce an improved chemical product havinggreater stability and which can be varied with respect to impurities andingredients over a greater range by comparison with the batch systemsfor combining such materials.

It will be further understood that other changes may be made in thedetails of construction, arrangement and operation without departingfrom the spirit of the invention, especially as defined in the followingclaims.

I claim:

1. The method of producing a mixed liquid fertilizer containing nitrogenand phosphorus in a predetermined ratio and in a continuous operation,comprising (a) feeding phosphoric acid under positive pressure in acontinuous stream at a substantially uniform rate to a reaction zone,

(b) feeding water in a continuous stream at a controllable rate andunder positive pressure to the reaction zone for admixture with thephosphoric acid in a predetermined ratio to provide for a predeterminedconcentration of phosphorus in solution in the system,

(c) feeding liquid ammonia in a continuous stream at a rate controlledby the pH of the final product and under positive pressure to thereaction zone for reaction with the diluted phosphoric acid solution toproduce ammonium phosphate,

(') expanding the mixture of materials into a reaction vessel forcompletion of the reaction,

(0") recompressing the mixture after reaction has been completed,

(d) extracting heat of reaction from the reaction product issuing fromthe reaction vessel to reduce the temperature of the reaction product tobelow the temperature for volatilization of any of the components, and

(e) separating the cooled reaction product into a product portion and aportion which is recycled through the system, the said extracting of theheat of reaction being accomplished at least in part by admixing therecycled portion with the partially reacted mixture issuing from thereaction zone and prior to expansion into the reaction vessel forimmediate reduction in temperature.

2. The method of producing a mixed liquid fertilizer containing nitrogenand phosphorus in a predetermined ratio and in a continuous operation,comprising (a) feeding phosphoric acid under positive pressure in acontinuous stream at a substantially uniform rate to a reaction zone,

(b) feeding water in a continuous stream at a controllable rate andunder positive pressure to the reaction zone for admixture with thephosphoric acid in a predetermined ratio to provide for a predeterminedconcentration of phosphorus in solution in the system,

(c) feeding liquid ammonia in a continuous stream at a rate controlledby the pH of the final product and under positive pressure to thereaction zone for reaction with the diluted phosphoric acid solution toproduce ammonium phosphate,

(d) controlling the rate of feed of ammonia to provide a reactionproduct having a neutral pH,

(d) expanding the mixture of materials into a reaction vessel forcompletion of the reaction,

(d") recompressing the mixture after reaction has been completed,

(e) extracting heat of reaction from the reaction product issuing fromthe reaction vessel to reduce the temperature of the reaction product tobelow the temperature for volatilization of any of the components, and

(f) separating the cooled reaction product into a product portion and aportion which is recycled through the system, the said extracting of theheat of reaction being accomplished at least in part by admixing therecycled portion with the partially reacted mixture issuing from thereaction zone and prior to expansion into the eaction vessel forimmediate reduction in temperature.

3. The method as claimed in claim 1 in which the flow rate of water iscontrolled responsive to the change in the flow rate of the phosphoricacid solution to maintain a constant ratio between the phosphoric acidand Water.

4. The method as claimed in claim 1 in which the flow rate of theammonia is controlled in response to the pH of the reaction productsubsequent to issuance from the reaction zone.

5. The method as claimed in claim 1 in which the tem perature of thereaction product immediately following issuance from the reaction zoneis maintained below F.

6. The method as claimed in claim 1 in which the ammonia is introducedas anhydrous ammonia.

7. The method as claimed in claim 1 in which the a1nmonia is introducedas ammonium hydroxide having NH present in amounts greater than 10 butless than 25 percent by weight.

8. The method as claimed in claim 1 in which the ammonia is added in anamount to produce a reaction product having a pH of about 6.8.

9. The method as claimed in claim 1 in which the reaction between thediluted phosphoric acid and ammonia is carried out under positivepressure thereby to accelerate the rate of reaction while militatingagainst the formation of volatiles.

10. The method as claimed in claim 1 in which the heat of reaction isadditionally extracted by heat exchange by circulating the reactionproduct through water cooled plates.

11. The method as claimed in claim 1 in which about 50-75 percent of thecooled reaction product is recirculated for combination with thereaction product issuing from the reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS2,917,380 Franklin Dec. 15, 1959 2,952,531 Bresee Sept. 13, 19602,969,280 Peck Jan. 24, 1961

1. THE METHOD OF PRODUCING A MIXED LIQUID FERTILIZER CONTAINING NITROGENAND PHOSPHORUS IN A PREDETERMINED RATIO AND IN A CONTINUOUS OPERATION,COMPRISING (A) FEEDING PHOSPHORIC ACID UNDER POSITIVE PRESSURE IN ACONTINUOUS STREAM AT A SUBSTANTIALLY UNIFORM RATE TO A REACTION ZONE,(B) FEEDING WATER IN A CONTINUOUS STREAM AT A CONTROLLABLE RATE ANDUNDER POSITIVE PRESSURE TO THE REACTION ZONE FOR ADMIXTURE WITH THEPHOSPHORIC ACID IN A PREDETERMINED RATIO TO PROVIDE FOR A PREDETERMINEDCONCENTRATION OF PHOSPHORUS IN SOLUTION IN THE SYSTEM, (C) FEEDINGLIQUID AMMONIA IN A CONTINUOUS STREAM AT A RATE CONTROLLED BY THE PH OFTHE FINAL PRODUCT BY UNDER POSITIVE PRESSURE TO THE REACTION ZONE FORREACTION WITH THE DILUTED PHOSPHORIC ACID SOLUTION TO PRODUCE AMMONIUMPHOSPHATE, (C'') EXPANDING THE MIXTURE OF MATERIALS INTO A REACTIONVESSEL FOR COMPLETION OF THE REACTION, (C") RECOMPRESSING THE MIXTUREAFTER REACTION HAS BEEN COMPLETED, (D) EXTRACTING HEAT OF REACTION FROMTHE REACTION PRODUCT ISSUING FROM THE REACTION VESSEL TO REDUCE THETEMPERATURE OF THE RACTION PRODUCT TO BELOW THE TEMPERATURE FORVOLATILIZATION OF ANY OF THE COMPONENTS, AND (E) SEPARATING THE COOLEDREACTION PRODUCT INTO A PRODUCT PORTION AND A PORTION WHICH IS RECYCLEDTHROUGH THE SYSTEM, THE SAID EXTRACTING OF THE HEAT OF REACTION BEINGACCOMPLISHED AT LEAST IN PART BY ADMIXING THE RECYCLED PORTION WITH THEPARTIALLY REACTED MIXTURE ISSUING FROM THE REACTION ZONE AND PRIOR TOEXPANSION INTO THE REACTION VESSEL FOR IMMEDIATE REDUCTION INTEMPERATURE.